Abrasive article



R. C. BENNER ET AL Y ABRASIVE'ARTICLE June 2, 1942.

Filed Jan. 22,v 1941 Nm @n R ..F www@ .,Y www w .A n www ,m @n S .M wm1E. A Y a( sbt@ mmf 0 Nm mi w@ @n Mw 4 i. l EL uw n l mm RR PatentedJune 2, 19442 ABRASIVE ARTICLE Raymond C. Benner and Romie L. Melton,

Niagara Falls, N.

asslznors to The Carborundum Company, Niagara Falls, N. Y.,a.,corporation of Delaware Application January 2z, 1941, serial No.315,513

13 claims. (o1. 511ss) 'I'his invention relates to flexible abrasivewebs and to methods of manufacturing said webs.

the like have been incorporated to impart de` sired properties thereto.

This application is a continuation-impart of one` flat surface of theweb with the amount of abrasive grain progressively diminishing as thedistance from that surface of the web becomes.

greater, there being little or no abrasive grain at the opposing or backsurface of the web. However, if desired the grain may be evenly anduniformly distributed as to amount or size throughou the web, or it maybe applied in such a manner our copending application Serial N o.343,150, filed June 29, 1940. I v p So-called coated abrasive articles,such as abrasive paper and cloth, discs and the like, are

old and well known in the art, but the present invention should not beconfusedwith such articles since it differs therefrom by the absence -ofthe conventional backing. It represents an tion, therefore, provides aflexible brous abrasive web material in which the abrasive grain isdistributed internally of a loose flimsy web of any suitable fibrousmaterial. Furthermore, the -abrading action is not connedtc asuperimposed layer of abrasive grains on the upper surface of the web',but the abrasive properties extend substantially all the way throughsaid web, there being no distinct line of demarcation between thefibrous web and the upper abrading surface. In other Words, webs havingan upper suraceapplim cation of abrasive grains as herein provided arelso constructed that the abrasive grain and adhesive binder permeatesand penetrates the 'brous web within the intersticesbetween theindividual fibers which then assist in holding the projectingabrasive'grain firmly in position.` Y

"Abrasive grain can be introduced entirely or Apartially within the webstructure in amount and character to suit the conditions and naturev ofthe intended use. For vexample',v the abrasive grain may be applied insuch a manner that there that the quantity of grain diminishes equallyfrom both surfaces of the web towards the interior. Similarly there maybe created an abrasive-containing web in which there is a gradation ofgrit size of abrasive grain through the web from one surface to theopposing surface. A coating of abrasive grain may also be applied, ifdesired, and adhesively secured to the top surface of the web, althoughthe last application of internally applied abrasive grain protrudes fromthe bres which help to hold it invposition and is sufficient toeiectively and eiliciently carry out polishing orgrinding operations. Asizing or surface application of adhesive may be applied to kthe layerof abrasive grains in order to anchor them more rmly in position.

Various modifying agents,` such as waterproofing compounds,anti-'friction agents, embrittling materials, exibilizers and otherfillers, may be incorporated in the web during manufacture in order torender the web resistant to water or impart specific desirablelropertiesto the web.

The amount and distribution of each specific modifying agent woulddepend upon the desired web properties and the particular portions ofthe web to be affected thereby.

In order that the invention may be more clearly set forth and made moreunderstandable in which:

Figure l is a greatly enlarged vertical crosssection through a fragmentof an abrasive web embodying the present invention;

Figure 2 is a similarly enlarged vertical crosssection of a modifiedform of abrasive web;

Figure-3 is still another modification of the invention; and i Figure 4is a diagrammatic side elevation, partly in section, showing one form ofapparatus for making abrasive webs according to the present invention.

In Figure 4 we have illustratedone form of apparatus which may beemployed in manufac- `turing abrasive webs comprising? a felt'ed fibrousmaterial with abrasive grains incorporated thereis a maximum amount ofabrasive particles at in and bonded with a suitable adhesive. Theparticular apparatus shown comprises ya plurality n web on the conveyorbelt.

of carding machines, suitably spaced apart and consisting of cardingrolls 2, stripper rolls 3 and combs 4, adapted to form and deliver anumber of fibrous membranes or laps 5, 6, I and 8 to the moving conveyorII.

The carded membranes or laps are delivered from the carding machines asflimsy webs of independent fibers generally parallel and looselyadhering together. These membranes may consist of any fibrous materialcapable of being carded into `web form or separable into individualfibers. Such materials include natural fibers, such as cotton, wool,jute, flax and asbestos-as well as the various synthetic fibers, such asglass wool, resinous and rubber-like fibrous substances. Any one ofthese fibrous materials maylbe used singly or two or more may be mixedin, any desired proportion. Cotton fibers have been found orifices orslots 9 in the floor I0 and onto a continuously moving conveyor belt I Iwhich is slightly wider than the width of the deposited'membranes. Asthe membranes pass through the slots 9 they are shielded from anyundesirable external influences, such as strong air currents, by thesurrounding sidewalls I2 and I3. The conveyor belt II is provided with asmooth outer surface and is supported at the opposite ends thereof- -bythe rolls I4 and I5, which are driven by any suitable means (not shown).The speed of the belt is synchronized-with the rate of feed of themembranes so as to prevent any appreciable strain or pull on the flimsymembranes during their deposition.

The individual laps 5, 6, l and 8 are applied successively to form acomposite layer of proper thickness and character. The number andarrangement of the carding assemblies will depend upon the desiredthickness and type of fibrous web produced.

Abrasive grains may-be incorporated internally' of the fibrous web byany one of several methods, such as by applying the grain to thedeposited membranes during the steps of building up the Suitableapparatus for `carrying out this step of the operation is illustrated inFigure 4 of the drawings, in which the abrasive grain is fed inregulated amounts from the several grain hoppers I6, I'I and I8, each of.which is provided with an adjustable feed gate I 9 and cooperatinggrain distributing roll 20. After one or more layers of fibrous membranehave been deposited on the carrier, the feed gate I9 of grain hopper I6is adjusted 'to feed a very thin stream of abrasive grain 2I onto thefibrous membrane. The next membrane 6 is then applied over this layer ofdeposited grain and the next increment of abrasive grains 2Ia depositedfrom the hopper II, the amount of grain being somewhat in excess of theamount of grain previously applied from hopper IS. In this way alternatelayers of abrasive grain and membranes or laps are deposited upon theconveyor belt and each successive application of abrasive grain may beheavier in amount than the previous application. If however, a uniformdistribution of grain through the web is desired, then the grain feedfrom the several feeding devices would be correspondingly adjusted. j

The particle size of the abrasive material may also be varied fromhopper to hopper, in which case the smallest particles may be appliedfrom the first bin I6 and-the size of the abrasive particles graduallyincreased in the successive bins I1 and I8. While only four bins forabrasive grains and four carding machines have been shown, it is to beunderstood that any number to be highly satisfactory in the presentprocess It is desirable, in certain instances, to incorporate anadhesive binder between the successive layers of fibrous membrane. Thisadhesive may be in powdered or liquid form and may be either a glue,resin, rubber or rubber-like material. Such adhesives may be applied inany suitable manner, such as, for example, mixing with the abrasivegrains and applying from the grain hoppers I6, II and I8, or separatehoppers and feed rolls may be utilized. Alternatively, the abrasivegrains may be individually coated with a suitable adhesive prior todeposition onto or inclusion Within the fibrous web. The adhesive mayalso be applied as a liquid in finely atomized form from suitable spraynozzles, provided the atomizing pressure is kept suciently low to avoiddisturbing the flimsy membranes.

The abrasive-containing fibrous web may be further modified by theapplication of various modifying agents during various stages of thebuilding up of the web in' the same way in which the adhesive is addedand in any required amount. For example, the web can be Waterproofed bythe application of a waterproofing agent to the membranes as they -lieon the carrier belt, or by the use of a waterproof adhesive binder.Again anti-friction ingredients of soapstone, graphite,

vand the like, can be similarly incorporated in those laps or membranesmaking up the portion of the web immediately adjacent the back surface.At any stage in the building up of the web, exibilizing, embrittling, orother agents may be similarly incorporated.

After the fibrous abrasive web I, with or without adhesive bindersand/or modifying agents, has been built up to the required thickness itis ready to be compacted to a greater density for added strength. At thesame time it is usually desirable to incorporate a liquid adhesivewithin said web to bond the compacted fibers and produce a dense webhaving a strength comparable to that of paper or cloth.

'I'he web I is initially compacted by the synchronously driven squeezerolls 22 and 23, which may be located near the terminus of thesupporting belt II. One or both of these rolls may have a resilientsurface or they m-ay have a roughened surface possessing a multiplicityof small projecting points. In either case the lndividual fibers of eachsuccessive lap or membrane are pressed down and around the base of eachindividual abrasive particle, securely anchoring it in place, andcausing the uppermost grains to project above the web surface to form anextremely sharp and fast cutting abrasive material. Y

Passing from the compacting rolls the web is fed onto a moving conveyorbelt 24, which is supportedgby the synchronously driven rolls 25v and2li, and delivered to the adhesive binder applying rolls 28, 29. Theliquid adhesive binder is contained in apan 30, which may bewaterjacketed and heated as required'. Revolving roll 29 is partiallyimmersed inthe adhesive and with each revolution transfers a quantity ofadhesive binder, determined by the setting of the adjustable scraper bar3|, into the fibrous web. Roll 28 applies sufficient pressure to nallycompact the loose fibrous web and aids in forcing the binder adhesive topermeate throughout the web. The surfaces of -both rolls 28, 29 arecovered with a resilient layerv of absorbing material. After theabrasive web is compacted and the proper amount of adhesive binderapplied therethrough,` it. is passed over asuction drum Il and `idlerroll 4| to a suitable chamber where it is In another modification of thepresent process the abrasive grains may-be applied to a previouslyformed lap or web. The formed lap may be moved past a singlegrainapplying means, such as the hopper 39 and its cooperating grainfeed roll I9, where the `entire amount of grain may be deposited on andinto the fibrous web at one application and then the adhesive binderapplied into the `abrasive filled lap by the. rolls dried or cured. Thischamber contains an endthe rack it may be out up into sheets, discs orbelts of suitable size or additional coatings may be appliedas will behereinafter described.

In a modified form of the present process, we may apply an additionallayer of abrasive grains to the vouter surface of the web after thefibrous abrasive web has been built up and compacted. In carrying outthis additional step of the process, `we apply `a layer of adhesive tothe outer side of the fibrous abrasive web by conventional adhesiveapplying means, such as the glue pan 30, adhesive roll 29, and apressure roll 28. A layer of abrasive grain of predetermined thick-'ness may be applied to the adhesively coated surface of the web by anyof the well known methods for applying abrasive grains, such as, forexample, an arrangement similar to the grain hopper i3 and the graindistributing roll Zit shown in Figure 4. The conventional sizing layeror adhesive is applied over the deposited layer of abrasive grains bythe usual adhesive rolls, similar to those used in spreading the'basecoating of adhesive.

The surface coating of abrasive grain may be applied at any time beforeor after partial or complete drying and curing of the abrasive lledfibrous web.

The abrasivegrain may be applied to vapreformed fibrous `web bygravitational forces, as described above, or by the more recentlydeveloped electrostatic, magnetic or mechanical methods of graindeposition. In these new grain deposition units, electrical and/ormechanical forces are utilized to orient the'elongated abrasive par- 28,29. Or, if desired, and particularly with the y finer abrasive materials(220 mesh in size and smaller) the grain may be uniformly mixed with theadhesive inthe pan 39 and both the abrasive and the adhesive binderapplied simultaneously to the already formed fibrous web. In either casethe abrasive grain is lodged in the open spaces within the web and heldin place by the surrounding fibers and adhesive.

Figure l is a greatly enlarged vertical crosssection of a fragment of anabrasive brous web made according toA the present invention, in whichweb the individual fibers 32 of the various membrances have been pressedaround the bases of the individual grains-33, rmly anchoring them inplace. The abrasive granules 33 have been distributed throughout the webin such a way that there is a maximum amount of abrasive ticles andproject them onto` the fibrous web so f that they are positioned withrtheir longer axis substantially perpendicular to the surface of theweb. For a more detailed description of suitable electrostaticapparatusfor orientation and projection of the abrasive granules onto anadhesively coated web, 'reference is made lto Patent No, 2,137,624,issued January 14, 1940, to R. L. Melton, R. C. Benner and H. P.Kirchner.' Suitable mechanical apparatus for the orientation anddeposition of abrasive grainsis described in Paten-tno. 2,141,653,issued December 27, 193s; and suitable magnetic orientation andprojection apparatus is illustrated and described in Patent No.2,254,531, issued September 2, '1941, to the same inventors. v

grain at the top surface 31 of the web with the amount of abrasive grainprogressively diminish-- ing to a minimumat the back surface 36,

Figure 2 shows a web fragment similar to that shown in Figure 1, inwhich an anti-friction agent 34 has been incorporated in that portion ofthe web nearest the back surface 36. An outer surface coating oiabrasive grain 35 has also been applied to the top side of the web.

Figure 3 is a modified web made according to the present inventionwherein the abrasive grains incorporated in the web show a gradation ofgrit size from the large grit grain 33o. at the top surface 3l of theweb down to the small grit size 33D nearest the back Sli of the web.Figures 1, 2 and 3 clearlyshow how the abrasive grains are held in placeby being intertwined by the long fibers whose lengths are'several timesthe dimension of the individual abrasive grit diarneters. Furthermore,the uppermost granules penetrate through and above the top layer ofmembrane fibers, which with the aid of an adhesive binder anchors themin such position that -the upper cutting edges are free for grinding andpolishing operations. l

We have found that the character of the abrasive material produced bythe herein-described process can be altered to any desired degree byvariations in the quantityand character of the adhesive binder`employed. By the addition of an embrittling agentor-the'use ofaresinous adhesive which cures to abrittle stage', we are able toproduce an article in which the fibrous materials break away and exposenew abrasivel grains duringy subsequent abrading operations. Thus `themulti-layer abrasive article acts in a manner similar to that of agrinding wheel. As

the surface granules become dulled and are broken away, the impregnatedand brittle fibers which areA exposed also break away and present a4fresh layer of sharp abrasive grains'at the Igrinding surface. Obviouslythe rate of breakdown of the fibrous membranecan be regulated vandcontrolled to any desired degree by changes inthe character and quantity`of the impregnating agent andthe degree of penetration into theindividual bers. The degree of penetration of the individual fibers maybe regulated by the material.

use of various textile wetting out Aagents which are well known in theindustry;

Very brittle characteristics may be imparted to the fibrous membrane byimpregnating with a liquid phenolic resin such as that commonly soldunder the trade name Durite S-2143." Sufiicient resin should beincorporated in the fibrous web so that the resin comprises from 30% to60% by weight of the impregnated fibrous The impregnated material maythen. be cured for approximately 2. hours ata temperature of 200.to 250F. If increased brittlenessy is desired, the length of the heattreatment may be extended` andthe curing temperature raised to 300 F.

A fibrous abrasive web possessing `a lesser degree of brittleness may beproduced by impregnating the fibers ofthe web with glue under conditionswhich will leave a dry glue residue of from 20% to 60% by weight of theimpregnated fibrous membrane.

Flexibilizing agents may be incorporated in a portion of the web ordistributed throughout, depending upon the type of product desired.Impregnation with a long oil synthetic resin varnish, such as that madeby Pratt and Lambert and designated by them as No. 1767, produces astrong and very .fiexible web. Sumcient varnish should be incorporatedso that it will comprise 20 to 40% by weight of the impregnated fibrousweb. The varnish may be cured by heating for approximately 2 hours at atemperature of 200 F.

In cases where a less flexible material is desired, we may use amaterial such as that sold under the trade name Bakelite varnish No.BV-6509 as the impregnant. Sufficient varnish should be incorporated intheweb so as to leave a dry residue of 20% to 40% by weight, and theimpregnated material cured from 2 to 4 hours at a temperature of 250 to280 F.

Various plasticizers, suchv as glycerine, dibutylphthalate, and the likemay be added to the varnish irnpregnating agents in order to increasetheir flexibility. The quantity of such material employed will dependupon the desired fiexibility characteristics of the finished product andmay, in some instances, amount to of the lcombined weight of the varnishand plasticizer.

We have also found that abrasive articles can be produced in which theouter surface, containing the maximum quantity of abrasive grain,`is ofa brittle character and the opposite side is of a flexible character.'I'hus one surface of the article functions most efficiently as anabrading device, while the opposite surface provides the necessaryflexibility and strength to permit use as a grinding belt, disc and thelike. Abrasive materials of such character may be produced by applyingan embrittling imprgnant to one side of the web 'and applying aflexibilizing impregnant to the opposite side.

Ther character of the abrasive web may be varied within wide limits byregulating the relative quantity of embrittling and flexibilizing agentsapplied to the opposite sides of the web and the depth of penetrationtherein.

The present invention readily lends itself to the creation of abrasivearticles of specific properties in definite controlled portions of thearticle without spreading such properties to other parts of the webWhere they are unnecessary or undesirable. Furthermore, the presentinvention provides an abrasive article which obviates the need for aseparate backing or other form of lamination, eliminating the weaknessof having a plurality of layers which are liable to split apart duringuse. The fibrous membrane structure, when compacted and reinforced withan adhesive bin'der, provides a strong supporting material and theabrasive grains included therein are firmly anchored in position. Thegrains are held in place byl what may be called a double anchorage,achieved by engagement of the individual fibers entwined around the baseof each individual grain andthe adhesion of the binder agent. Anotherimportant advantage is that an abrasive -article made in accordance withthe invention possesses a resiliency and fiexibility which isimpractical to obtain with abrasive coated paper or cloth.A l

While we have specificallyillustrated and described the preferredembodiment of our invention, it is to be understood that the inventionmay be otherwise embodied and practised within the scope of thefollowing claims.

We claim: 1

l. A flexible abrasive web of felted fibrous materials impregnated withsuitable adhesive binder and having abrasive grain distributedinternally of the web, said web having an abrasive grain contentprogressively greater from one surface of the web to the opposing websurface.

2. A exible abrasive web of felted fibrous materials impregnated withsuitable adhesive binder and having abrasive grain distributedinternally of the web, said abrasive grain being so distributed that theamount of abrasive grain within said Web varies inversely as thedistance from the upper surface of said web.

3. A flexible abrasive web of felted fibrous materials impregnated withsuitable adhesive binder and having abrasive grain distributedlinternally of the web, said abrasive grain being so distributed that theamount of abrasive grain within said web varies .inversely as thedistance from the upper surface of said web, the upper surface of saidweb having a substantially external coating of abrasive grain adhesivelysecured thereto.

4. A exible abrasive web of felted fibrous materials impregnated withsuitable adhesive binder and having abrasive grain distributedinternally of the web s'O that the amount of abrasive grain within saidweb varies inversely as the distance from the upper surface of said web,said web being rendered substantially resistant to water byincorporation of a waterproofing agent within the web.

5. A flexible abrasive web of felted fibrous materials impregnated withsuitable adhesive binder and having abrasive grain distributedinternally of the web so that the amount of abrasive grain within saidweb varies inversely as the distance from the upper surface of said web,the upper surface of the web having a substantially external coating ofabrasive grain adhesively secured thereto, said web being renderedsubstantially water resistant by presence of a waterproofing agent inthe web.

6. A flexible abrasive web of felted fibrous materials impregnated withsuitable adhesive binder and having abrasive grain distributedinternally of the web, said abrasive grain being so distributed that thesize of the abrasive grain within said web varies inversely as thedistance from the upper surface of said web.

7. An abrasive article comprising a plurality of sive being adapted toretain the web in its compacted form. l V

8. An abrasive article comprising a compacted web of dry-laid cardablefibers, abrasive particles distributed internallyof said web and anadhesive binder incorporated within said web, said adhesive beingadapted to retain the web in its compacted form and to anchor theabrasive grains in position. .l

9. A flexible abrasive web of dry-laid cardable, felted, iibrousmaterials permeated' with a suitable adhesive binder/ and havingabrasive grain distributed internally and at the surface of the web,said surface grain being partially held in place by disposition withinthe brous structure of said web.

10. A flexible abrasive web of feited fibrous materials permeated with asuitable adhesive binder and having abrasive grain distributedinternally and at the surface of. the web, said web carded feltedfibrous materials permeated with a mutable adhesive binder and havingabrasive grain distributed internally and at the surface of the web, theindividual fibers of said web being impregnated with an embrittlingagent so as to render them appreciably friable when'used 41in abradinsoperations. l

- 12. An abrasive article comprising a web of felted fibrous materialspermeated with a suitable adhesive binder and having abrasive graindistributed internally and at the surface of the web, the individualfibers contained'in one surface of said web being impregnated with anembrittling agent to render them friable and the opposite surface ofsaid web permeated with a flexibilizing agent.

-13. A flexible abrasive web of Afelted fibrous materials impregnated'with suitable adhesive binder and having abrasive grain distributedinternally of the web. said abrasive grain being so distributed that theamount of abrasive grain within said web gradually diminishes lfrom bothsurfaces of the web toward"the interior of the web,

RAYMOND C. BENNER. ROMIE' L. MELTON.

